1. Field of the Invention
The present invention relates to a nucleic acid detection device used to a target nucleic acid detection utilizing the electrochemical response of a nucleic acid recognition body.
2. Description of the Related Art
As genetic engineering develops in recent years, disease diagnosis or prevention using a gene has become possible in the medical field. This is called gene diagnosis. Detecting a human gene defect or change that causes a disease allows the disease to be diagnosed or predicted precritically or at its very early stage. Along with human genome decoding, researches on the relationship between the genotype and disease advance. Treatments that match the genotype of the individual patients (tailor-made medical care) are being put into practice. Accordingly, it is very important to detect a gene and determine a genotype simply.
Examples of nucleic acid detection methods include a method using a radioisotope and a method using a fluorescent dye label. The former method can perform detection only at limited locations and requires cumbersome operation. The latter method requires an expensive apparatus to detect a fluorescent dye.
Besides these techniques, another technique has been established. According to this technique, a sample nucleic acid is hybridized with a nucleic acid probe immobilized to the surface of an electrode. Then, a nucleic acid recognition body is added and electrochemically detected. The technique of electrochemically detecting a nucleic acid is suitable to “Lab-on-a-chip” of causing reactions on a single chip. Hence, this technique has been under development in a variety of applications.
Various types of nucleic acid recognition bodies are available. Various types of nucleic acid recognition bodies are exists. For example double stranded nucleic acid recognition body which recognizes the double stranded nucleic acid. Assume that the electromechanical response of the nucleic acid recognition body is to be measured to detect the presence/absence of a target nucleic acid. In this case, whether the recognition body is adsorbed by a double stranded nucleic acid, a single stranded nucleic acid, or an electrode surface cannot be discriminated. Hence, in addition to the electrochemical response caused by hybridization of the target nucleic acid, a background electrochemical response (reference value, negative control) caused by adsorption to the single stranded nucleic acid or the electrode surface exists. This is regarded as the defect of the scheme that detects a nucleic acid by using the electrochemical response of the nucleic acid target body in comparison with the scheme that detects a nucleic acid with a fluorescent dye. If the nucleic acid recognition body concentration is high, the background electrochemical response (reference value) increases. If the nucleic acid recognition body concentration is low, the electrochemical response caused by hybridization decreases. Hence, the nucleic acid recognition body concentration must be so set as to fall within an optimal concentration range.
The nucleic acid hybridization is easily influenced by the temperature, salt concentration, the pH of the solution, the flow velocity of the solution, and the like. The nucleic acid recognition body should be reacted in such a condition that a nucleic acid bond in which the target nucleic acid hybridizes with the nucleic acid probe will not be dissociated.
According to one nucleic acid detection device that supplies a nucleic acid recognition body by utilizing a flow channel, in order to increase the length of the flow channel, curved portions are formed midway along the flow channel so the flow channel meanders. In this nucleic acid detection device, the curve portions that exist midway along the flow channel disorder the flow of solution. The disordered flow of solution decreases the detection accuracy.